bn_shift.c

/* crypto/bn/bn_shift.c *//* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. * * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to. The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code. The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). * * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * "This product includes cryptographic software written by * Eric Young (eay@cryptsoft.com)" * The word 'cryptographic' can be left out if the rouines from the library * being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from * the apps directory (application code) you must include an acknowledgement: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" * * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */#include <stdio.h>#include "cryptlib.h"#include "bn_lcl.h"int BN_lshift1(BIGNUM *r, constBIGNUM *a)
{
register BN_ULONG *ap,*rp,t,c;
int i;
bn_check_top(r);
bn_check_top(a);
if (r != a)
{
r->neg=a->neg;
if (bn_wexpand(r,a->top+1) == NULL) return(0);
r->top=a->top;
}
else
{
if (bn_wexpand(r,a->top+1) == NULL) return(0);
}
ap=a->d;
rp=r->d;
c=0;
for (i=0; i<a->top; i++)
{
t= *(ap++);
*(rp++)=((t<<1)|c)&BN_MASK2;
c=(t & BN_TBIT)?1:0;
}
if (c)
{
*rp=1;
r->top++;
}
bn_check_top(r);
return(1);
}
int BN_rshift1(BIGNUM *r, constBIGNUM *a)
{
BN_ULONG *ap,*rp,t,c;
int i;
bn_check_top(r);
bn_check_top(a);
if (BN_is_zero(a))
{
BN_zero(r);
return(1);
}
if (a != r)
{
if (bn_wexpand(r,a->top) == NULL) return(0);
r->top=a->top;
r->neg=a->neg;
}
ap=a->d;
rp=r->d;
c=0;
for (i=a->top-1; i>=0; i--)
{
t=ap[i];
rp[i]=((t>>1)&BN_MASK2)|c;
c=(t&1)?BN_TBIT:0;
}
bn_correct_top(r);
bn_check_top(r);
return(1);
}
int BN_lshift(BIGNUM *r, constBIGNUM *a, int n)
{
int i,nw,lb,rb;
BN_ULONG *t,*f;
BN_ULONG l;
bn_check_top(r);
bn_check_top(a);
r->neg=a->neg;
nw=n/BN_BITS2;
if (bn_wexpand(r,a->top+nw+1) == NULL) return(0);
lb=n%BN_BITS2;
rb=BN_BITS2-lb;
f=a->d;
t=r->d;
t[a->top+nw]=0;
if (lb == 0)
for (i=a->top-1; i>=0; i--)
t[nw+i]=f[i];
elsefor (i=a->top-1; i>=0; i--)
{
l=f[i];
t[nw+i+1]|=(l>>rb)&BN_MASK2;
t[nw+i]=(l<<lb)&BN_MASK2;
}
memset(t,0,nw*sizeof(t[0]));
/* for (i=0; i<nw; i++) t[i]=0;*/
r->top=a->top+nw+1;
bn_correct_top(r);
bn_check_top(r);
return(1);
}
int BN_rshift(BIGNUM *r, constBIGNUM *a, int n)
{
int i,j,nw,lb,rb;
BN_ULONG *t,*f;
BN_ULONG l,tmp;
bn_check_top(r);
bn_check_top(a);
nw=n/BN_BITS2;
rb=n%BN_BITS2;
lb=BN_BITS2-rb;
if (nw >= a->top || a->top == 0)
{
BN_zero(r);
return(1);
}
if (r != a)
{
r->neg=a->neg;
if (bn_wexpand(r,a->top-nw+1) == NULL) return(0);
}
else
{
if (n == 0)
return 1; /* or the copying loop will go berserk */
}
f= &(a->d[nw]);
t=r->d;
j=a->top-nw;
r->top=j;
if (rb == 0)
{
for (i=j; i != 0; i--)
*(t++)= *(f++);
}
else
{
l= *(f++);
for (i=j-1; i != 0; i--)
{
tmp =(l>>rb)&BN_MASK2;
l= *(f++);
*(t++) =(tmp|(l<<lb))&BN_MASK2;
}
*(t++) =(l>>rb)&BN_MASK2;
}
bn_correct_top(r);
bn_check_top(r);
return(1);
}